Conventionally, there has been known a particle detection system which includes a particle sensor for detecting particles such as soot contained in a gas under measurement. A specific example of such a particle detection system is a particle detection system which produces ions by means of corona discharge, and electrifies particles (soot, etc.) contained in exhaust gas through use of the produced ions, to thereby detect the amount of particles contained in the exhaust gas. As an example of such a particle detection system, Patent Document 1 discloses a particle detection system which is mounted on a vehicle having a diesel engine and in which a particle sensor 100 and a sensor drive section 110 for controlling the same are connected through a cable 120.
Also, Patent Documents 2 and 3 disclose a particle detection system whose detection section includes a pair of electrodes overlapping each other to form the shape of a double-wall tube and in which, after PM agglomerates (PM structures (particulate matter structures)); i.e., particles adhering to the surface of an electrode, are previously formed through use of particles contained in a gas under measurement flowing through the space between the electrodes, the gas under measurement is caused to flow through the space between the electrodes, and a high voltage is applied between the electrodes. Thus, electrified PM agglomerates move between the electrodes, and the particles are detected through use of the electrified PM agglomerates.
In these particle detection systems, when particles such as soot adhere to the surface of an insulating member provided in a particle sensor and deteriorate the insulation performance of the insulating member at the surface, the detection performance may deteriorate; for example, the particle detection accuracy may lower or the detection may become impossible. In order to overcome such a problem, there has been proposed a particle detection system in which its particle sensor has a heater for heating the surface of the insulating member, and particles such as soot adhering to the surface of the insulating member are burned and removed by heating by the heater. For example, in the particle detection system of Patent Document 1, a heater pattern 380 is provided in a sensor unit 300 formed of an insulating ceramic (insulating material) and provided in the particle sensor 100. This heater pattern 380 heats the entirety of the sensor unit 300 to 550 to 600° C. to thereby burn soot adhering to a first electrode 322 of a discharge pattern 320, etc.